1. Field of the Invention
The present invention relates to a mechanism for adjustable installation of a plate-like member, particularly a plate-like member such as a reflector in order to make an effective surface of this member facing in a desired direction and more particularly to such mechanism suitable to adjust the direction in which the effective surface of an optical scanner""s reflector faces.
2. Description of the Related Art
An optical scanner used in an image forming apparatus such as copying machine or printer is generally arranged so that a laser beam emitted from a laser source and containing image information is appropriately toned, then enters deflector means such as a polygon mirror and the laser beam thus deflected irradiates and scans an image carrier as an object to be scanned, for example, a photosensitive drum and forms an electrostatic latent image on this image carrier. This electrostatic latent image is developed with toner to form a toner image, which is then transferred to a transfer medium such as recording paper to form a visible image thereon. As color image forming apparatus, for example, color copying machine or color printer, the image forming apparatus of tandem type has been widely used. In the image forming apparatus of this type, a plurality of image carriers such as photosensitive drums are arranged side by side so that electrostatic latent images may be formed on the respective image carriers as the laser beams containing the image data colored in yellow (Y), magenta (M), cyan (C) and black (BK), respectively, irradiate and scan said respective image carriers. These electrostatic latent images are developed by respective particular kinds of toner to form respective toner images which are then successively transferred to the transfer medium such as recording paper travelling in the direction of the image carriers"" side by side arrangement to form color images thereon.
Demand for pluralization of the light beam for scanning and the scanning unit has increased as high-speed copying machines and printers have come widely in use. Additionally, in order to ensure the formed image to be distinct, optical characteristics of these plural scanning light beams as well as the scanning characteristics of these plural scanning units must meet the predetermined requirements and the characteristics of these plural units must be uniform. To ensure the required optical characteristics and the scanning characteristics, installation precision of the optical members constituting the optical scanner must be sufficiently high to achieve the proper operative association one with another. Particularly, even a slight error in the reflecting direction of the reflector or variation in the installed state will deteriorate the optical characteristics as well as the scanning characteristics. To avoid such problems, the reflecting direction of the reflector should be adjusted to a high precision.
The mechanism for adjustable installation of a reflector is well known, in which the spacer as thin as possible, for example, a mica plate is disposed between the reflector and the bracket on which the reflector is mounted and thereby said reflector is adjustably tilted. As an example of such mechanism, so-called mirror adjusting mechanism is described in Japanese Utility Model Application Disclosure Gazette No. 1993-33108. This mirror adjusting mechanism of prior art comprises: a mirror frame; a supporting piece mounted on an end of said mirror frame so that said supporting piece may bear against a reflective surface of a mirror; an adjusting plate is rotatably mounted on said adjusting plate so that said adjusting plate may bear against said reflective surface of said mirror; an adjusting member mounted on said adjusting plate to adjust an angular position of said adjusting plate; and a biasing member adapted to bear against a rear surface of said mirror frame and thereby to bias said mirror. Said adjusting plate is adjustably rotated by said adjusting member to swing the mirror around its longitudinal axis and thereby to change a direction in which the reflective surface thereof faces.
These conventional adjusting mechanisms as have been described above are inevitably accompanied with problems. In the case of the mechanism adapted to tilt the reflector by interposition of the spacer, it is certainly possible to adjust a tilt of the reflector omni-directionally. However, the extremely thin spacer makes operation of adjustment troublesome. In addition, a clamping force of the set screw used to fix the reflector is not constant and consequently it is sometimes impossible to make the reflector face in the desired direction, in spite of interposition of said spacer. In other words, no quantitative adjustment is impossible and the adjusting effect may largely depend on working accuracy of the components such as the spacer, the reflector and the brackets.
The mirror adjusting mechanism described in said Japanese Utility Model Application Disclosure Gazette No. 1993-33108 is adapted to rotate the adjusting plate by screwing-in or out an adjusting screw and by adjusting a movement of the adjusting screw back and forth, no fine adjustment is possible since the adjustment largely depends on a pitch of the adjusting screw.
While it may be contemplated to use an eccentric pin as the adjusting member to perform such adjustment, a variation occurring in a tilt of the plate-like member every time the operation of adjustment is carried out is too large to meet the recently demanded requirements for the high precision of adjustment.
In view of the problems as have been described above, it is a principal object of the present invention to provide a mechanism for adjustable installation of a plate-like member particularly suitable for a reflector in an optical scanner improved so that not only the quantitative adjustment but also a fine adjustment can be achieved.
The object set forth above is achieved, according to an aspect of this invention, by a mechanism for adjustable installation of a plate-like member comprising a cam member located at one of longitudinally opposite ends of said plate-like member aside to one of transversely opposite ends of said plate-like member so that a cam curve of said cam member may be normally kept in contact with one surface of said plate-like member, said plate-like member is pivotally supported at the other of said transversely opposite ends, biasing means adapted to bias said other surface so that said one surface may be normally kept in contact with said cam curve and actuator means adapted to rotate said cam member and thereby to alter a position of the plate-like member at which said cam curve comes in contact with said one surface.
The position of the plate-like member at which the cam curve comes in contact with the plate-like member is changed as said cam member is rotatably driven by said actuator means, With a consequence, one of the transversely opposite side edges of said plate-like member has its position changed and the direction in which the effective surface of said plate-like member faces is also changed. Under the effect of the biasing means, the plate-like member is normally kept in contact with the cam curve and reliably moved by said cam curve. Movement of the plate-like member by the cam curve advantageously enables the adjustable installation of said plate-like member to be continuously and finely achieved so far as said cam curve is appropriately configured.
According to one preferred embodiment of this invention said cam member moves in the axial direction of its rotational shaft as said cam member rotates.
In the case of the cam curve configured so as to intersect a plane orthogonal to the rotational axis of the cam member, the position of the plate-like member at which the latter comes in contact with the cam curve inevitably varies as the cam member rotates. For such arrangement, there is an apprehension that a position variation for the adjustable installation of the plate-like member might be unstable. The arrangement of the invention eliminates such apprehension by moving the cam member in the direction of its rotational axis in accordance with the configuration of the cam curve and thereby ensuring the constant position of the plate-like member at which the latter comes in contact with the cam curve. In this way, the position variation for the adjustable installation of the plate-like member can be reliably stabilized.
According to another preferred embodiment of this invention, said actuator means comprises an actuator screw engaged with said cam member, said actuator screw having its feed direction substantially coincident with said rotational shaft of said cam member and being formed with an appropriate cam curve, and said mechanism further comprises a guide member adapted to be engaged with said cam curve.
Rotation of the actuator screw causes the cam member engaged with said actuator screw to move back or forth depending on the direction in which said actuator screw is rotated. The cam member moves back or forth as it is rotated under a restriction by said cam curve with which the guide member is engaged. Rotation of the cam member continuously varies the position of the plate-like member at which the latter comes in contact with the cam curve formed in the cam member and thereby adjustably varies the state in which said plate-like member is installed. In addition, said position can be maintained constant so far as the cam curve of the cam member is appropriately configured.
The object set forth above is achieved, according to another aspect of this invention, by a mechanism for adjustable installation of a plate-like member comprising a pair of cam members located at one of longitudinally opposite ends of said plate-like member so that respective cam curves of said cam members may be normally kept in contact with one surface of said plate-like member, biasing means adapted to bias said other surface so that said one surface may be normally kept in contact with said cam curves, and actuator means adapted to rotate said cam members and thereby to alter positions of the plate-like member at which said cam curves come in contact with said one surface.
Specifically, the respective cam curves of said cam members come in contact with the plate-like member at its transversely opposite ends on one of its longitudinally opposite ends. In this way, the installation of the plate-like member can be adjusted at its transversely opposite side edges more finely than in the case of the single cam member.
According to one preferred embodiment of this invention on said another aspect, said pair of cam members have their rotational shafts extending substantially in parallel to each other so that transmission means may transmit rotation of the one cam member to the other cam member and cause said other cam member to rotate in synchronization with said one cam member.
According to another preferred embodiment of this invention, said transmission means is provided in the form of a gear system or a belt gearing system.
Rotation of the one cam member is transmitted to the other cam member by said transmission means so that said other cam member is rotated synchronization with said one cam member. It is unnecessary to actuate the pair of cam members separately and the operation of adjustment is correspondingly simplified. The pair of cam members is preferably arranged so that the axes of these cam members may extend substantially in parallel to the longitudinal direction of the plate-like member. The transmission means may be selected from a belt gear system, a gear system and the like.
According to still another preferred embodiment of this invention, said pair of cam members are coaxial to each other and have different cam curves, respectively, so that these cam members may be rotatably driven by said actuator means.
The shaft supporting the pair of cam members may be rotated to rotate these cam members together. The respective cam members have the cam curves of different configurations and therefore the plate-like member is differentially moved at its transversely opposite side edges as said pair of cam members are rotated. The direction in which the effective surface of the plate-like member faces can be varied by such differential movement. It should be understood that said axis preferably extends substantially in parallel to the transverse direction of the plate-like member.
According to further another preferred embodiment of this invention, said pair of cam members have the cam curves which are identical to each other but phase-shifted from each other so that these cam members may be rotatably driven by said actuator means.
Compared to the case in which the respective cam members have the cam curves configured differentially from each other, combination of the cam members having the respective cam curves identically configured requires less time and labor for working of them and facilitates the quality control thereof.
According to an additional preferred embodiment of this invention, said cam members move in the axial direction of their rotational shafts as said cam members rotate.
According to further additional preferred embodiment of this invention, said actuator means comprises an actuator screw engaged with one of said cam members, said actuator screw having its feed direction substantially coincident with said rotational shafts of said cam members and at least one of said pair of cam members being formed with an appropriate cam curve, and wherein said mechanism further comprises a guide member adapted to be engaged with said cam curve.
According to still additional preferred embodiment of this invention, the casing adapted to receive said cam member(s) is movable in the direction orthogonal to the longitudinal direction of said plate-like member.
The cam members and therefore the cam curves thereof have their positions varied as the cam members move transversely of the longitudinal direction of the plate-like member. Thus the positions at which the plate-like member comes in contact with the respective cam curves. In this way, said plate-like member can be moved, for example, in the direction orthogonal to the surface of said plate-like member or transversely of said plate-like member. By moving the plate-like member in such direction, the position of the plate-like member relative to the remaining parts can be easily adjusted. Particularly in the optical sensor, the optical path length can be easily adjusted and the desired optical properties can be easily ensured. After has been moved in this manner, the cam member may be further rotated to adjust the state of the installation.
According to a preferred specific embodiment of this invention, further comprising follower rod(s) each having one end adapted to be normally kept in contact with said cam curve(s) of said cam member(s) and the other end adapted to be normally kept in contact with said plate-like member.
Assumed that the cam member itself is made of a thin plate or the like contoured by the cam curve, the plate-like member can be stably adjusted since a substantial point-contact is established between the cam curve and the plate-like member. However, there is an apprehension that the thin plate might suffer from a shortage of its strength. To overcome this problem, the cam member is shaped in a cylinder or the like formed on its outer surface with the cam curve so that one end of said follower rod may be normally kept in contact with said cam curve and the other end may be normally kept in contact with the plate-like member. In this way, the point-contact is established between the cam curve and the plate-like member by said follower rod extending between these two member and thereby operation of said plate-like member can be stabilized.
According to another preferred specific embodiment, said plate-like member is a reflector installed within an optical apparatus.
By providing the reflector in the optical scanner with the mechanism according to this invention, the reflecting direction of this reflector can be easily and quantitatively adjusted. The state in which the reflector is installed in the optical scanner can be thereby adjusted with a high precision and the desired various factors of the optical scanner such as the optical characteristics and the scanning characteristics can be ensured and maintained.